Field
The present disclosure relates to communication networks. More specifically, the present disclosure relates to a system and a method for fast multicast recovery for a rebooting switch.
Related Art
The exponential growth of the Internet has made it a popular delivery medium for a variety of applications running on physical and virtual devices. Such applications have brought with them an increasing demand for bandwidth. As a result, equipment vendors race to build larger and faster switches with versatile capabilities, such as efficient multicast forwarding. However, the capabilities of a switch cannot grow infinitely. It is limited by physical space, power consumption, and design complexity, to name a few factors. Furthermore, switches with higher capability are usually more complex and expensive. As a result, increasing efficiency in existing capabilities of a switch adds significant value proposition.
Typically, a multicast protocol, such as protocol Independent Multicast (PIM), relies on the knowledge of the receivers, a data source, and a rendezvous point (RP) to operate. A switch running the multicast protocol usually processes join requests received from end devices to determine the receivers. The switch then uses join and prune messages to discover the data source, the RP, and outgoing interfaces. The switch uses such information to construct the multicast protocol states to participate in the multicast forwarding.
If the switch suffers an unplanned reboot (e.g., due to a power failure), the line cards of the switch can also lose their power supply. As a result, the switch goes through a complete power cycle, leading to a disruption in multicast forwarding. If this failure propagates to a plurality of switches (e.g., also to the backup switches), multicast data forwarding in the entire network can be disrupted. Under such circumstances, the convergence time for the multicast protocol is constrained by the time needed to rebuild the multicast protocol state. This rebuilding involves convergence of information associated with the receivers, the source, and the RP based on join and prune message processing. Furthermore, if the multicast protocol operates based on a unicast protocol (e.g., the routing protocol for the switch), this convergence time is in addition to the convergence time of unicast protocol. As a result, after the reboot, the switch can only resume its multicast forwarding after the convergence of both unicast and multicast protocols running on the switch.
While multicast forwarding brings many desirable features to a switch, some issues remain unsolved in facilitating fast recovery of the multicast states of a switch in the event of an unplanned reboot.